This invention relates to switching systems, and more particularly to optimization of communication transmissions in such switching systems when seeking information.
Certain IP (Internet Protocol) and ATM (Asynchronous Transfer Mode) applications require that a broadcast message be sent to a group of potential receivers in order to obtain some information from one or more of the receivers. In IP, for example, ARP requests are made for the specific task of converting an Ethernet address to the corresponding IP address. The request is broadcast on the Ethernet, and the correct recipient responds with an ARP message. The results are usually stored in a cache for future reference. Such caches typically are caused to "age" so that entries which are older than some preselected threshold may be removed. This intends to insure that stale, and perhaps no longer valid, data is not being used, and to insure that the memory occupied by the cache does not grow beyond some preselected bound. Accordingly, information-seeking broadcasts are not out of the ordinary.
In switched architectures, such as ATM, for example, there are no inherent means for carrying out broadcasts. One configuration that is available, pursuant to agreed-upon standards, is a LAN emulation (LANE) architecture where one node serves as a Broadcast and Unknown Server (BUS). In such an arrangement, depicted in FIG. 1, a broadcast is implemented by the BUS sending packets to the entire set of nodes, effectively at the same time, or to groups of nodes, seriatim. The broadcast is maintained as a collection of point to multi-point virtual circuits.
Such an approach to broadcasting represents a fairly intensive use of resources. Accordingly, it is desirable to implement such broadcasting in a manner that efficiently utilizes the available resources.